Control knob



FIG. 1 is a front perspective view of a control knob showing my new design;

FIG. 2 is an enlarged top plan view thereof;

FIG. 3 is an enlarged front elevational view thereof;

FIG. 4 is an enlarged right side elevational view thereof;

FIG. 5 is an enlarged bottom plan view thereof; and,

FIG. 6 is an enlarged left side elevational view thereof.

The stem illustrated in phantom is for environment only and does not form a part of the design. 

The ornamental design for a control knob, as shown and described. 